The present invention relates to operation of an engine with aftertreatment, and more particularly, but not exclusively relates to using internal exhaust gas recirculation (EGR) to lower engine out NOx emissions at times when aftreatment system efficiency is low and to control aftertreatment system efficiency during engine operation.
Various aftertreatment subsystems have been developed to control exhaust emissions from internal combustion engines. The performance of aftertreatment subsystems often varies with temperature, which has led to the development of various thermal management schemes. Unfortunately, these schemes can require multiple additional components to implement and therefore increase the cost of the system, and often fall short of performance goals when the engine is initially started or operates with a relatively light load because desired temperature levels and other operating conditions to efficiently operate aftertreatment systems are difficult to reliably attain. Thus, there is a continuing demand for further contributions in this area of technology.